Sound Spectrum Analyzer

Real-time FFT spectrum and spectrogram view with stereo, mid, and side modes. Measure peak, RMS, crest factor, L/R correlation, dominant frequency, and band energy.

Dominant Frequency —

Note —

Correlation —

Frozen

Press Start Mic Analysis or Upload Audio File to begin.

View

Smoothing 0.70

FFT Size

Peak

—

RMS

—

Crest Factor

—

Clipping

Band Energy

Low (20–250 Hz)

—

Mid (250 Hz – 4 kHz)

—

High (4–20 kHz)

—

What is a Spectrum Analyzer?

A spectrum analyzer shows how much energy is present at each frequency in a signal. Sound is made up of many frequencies played simultaneously — bass, midrange, and treble. A spectrum analyzer splits this up visually so you can see exactly what is in the sound.

This tool runs a Fast Fourier Transform (FFT) on your microphone input (or an uploaded audio file) hundreds of times per second. The result is displayed either as a live bar graph (Spectrum) or as a scrolling heat-map over time (Spectrogram).

Display Modes

Spectrum

Live bar/line graph of current frequency content. In Stereo view, left (red) and right (green) channels are drawn separately so you can see channel differences and stereo imaging issues at a glance.

Spectrogram

Scrolling heat-map where the horizontal axis is time, the vertical axis is frequency, and color intensity is amplitude. Great for catching transients, identifying hum/whistle frequencies, and visualizing musical phrases.

View Modes

Stereo (L/R)

Displays left and right channels independently. Useful for checking mix balance or detecting channel problems.

Mid (Mono)

Sum of left + right divided by 2 — the shared centre content. Matches how most mono playback systems will hear your audio.

Side (Stereo Diff)

Left minus right — reveals only the stereo difference. A near-silent Side trace means the signal is almost mono.

What Can You Use It For?

Find room resonances and acoustic problems
Check speaker and headphone frequency response
Identify electrical hum (50 Hz / 60 Hz) and HVAC noise
Analyze music mixing and tonal balance
Tune instruments by watching fundamental frequencies and the note readout
Diagnose distortion, clipping, and overloaded channels
Visualize transient attacks on the spectrogram
Verify stereo imaging with the Side view

What the Stats Mean

Peak dB — the loudest individual frequency bin at this instant. Rises with bright, percussive content.

RMS dB — Root Mean Square of the signal, a perceptually stable loudness measurement.

Crest Factor — ratio of peak to RMS. High values (>15 dB) indicate dynamic, punchy audio. Low values (<6 dB) suggest heavy compression or distortion.

Correlation — from −1 (fully out of phase) to +1 (mono). Near 0 means a wide stereo field; negative values can indicate phase problems that disappear in mono.

Clipping — turns red when the input signal is at or near digital maximum. Sustained clipping sounds like harsh distortion and should be avoided.

Frequently Asked Questions

20 Hz to 20 kHz — the full range of human hearing. Your microphone may not respond equally across the whole range, but the analyzer displays whatever energy is captured.

FFT size determines how many frequency bins the signal is split into. Larger sizes (8192, 16384) give more frequency detail but respond slower. Smaller sizes (1024, 2048) react faster but show less detail. 4096 is a good default.

Spectrum shows a snapshot of energy at each frequency right now. Spectrogram is a scrolling 2D picture where the horizontal axis is time, the vertical axis is frequency, and color intensity is amplitude — so you can see how the spectrum changes over seconds or minutes.

Yes. Click Upload Audio File, pick any audio your browser can decode (WAV, MP3, M4A, OGG, FLAC, etc.), then press Play. Nothing is uploaded — decoding and analysis happen entirely in your browser.

Mid is the sum of left and right channels, representing the centered/mono content. Side is left minus right — only what differs between the channels. Side shows the "stereo-ness" of the signal; a silent Side means it is nearly mono.

Negative correlation means the two channels are partly out of phase. Small negative values are normal on wide stereo mixes, but strongly negative values signal phase problems that could cancel out when the signal is collapsed to mono.

The strongest frequency is matched to the nearest musical note and displayed with its cents offset. A reading of "A4 +0 cents" means the dominant pitch is perfectly in tune at 440 Hz. "A4 −15 cents" means it is 15 cents flat.

Yes. Press the Freeze button to hold the current view, then Screenshot to download a PNG of exactly what is on screen. Works for both Spectrum and Spectrogram modes.